drivers/net/vsc9953: Add commands for VLAN ingress filtering

drivers/net/vsc9953: Add commands for VLAN ingress filtering

The command:
ethsw [port <port_no>] ingress filtering
     { [help] | show | enable | disable }
  - enable/disable VLAN ingress filtering on port

can be used to enable/disable/show VLAN ingress filtering on a port.
This command has also been added to the ethsw generic parser
from common/cmd_ethsw.c

Signed-off-by: Johnson Leung <johnson.leung@freescale.com>
Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@freescale.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
Reviewed-by: York Sun <yorksun@freescale.com>